The present invention relates to a programmable control apparatus with printed circuit boards contained in a housing. Such control apparatuses serve to the programmed control of machine tools and installations, production processes and similar. Known control apparatuses of this kind comprise metal housings in which the printed circuit boards are fixedly contained. An exchange of these printed circuit boards is not possible. Metal housings provide for a good screening against parasitics fields but they are expensive to produce. For the rest, the accessibility of the printed boards by known apparatuses is unsatisfactory, that is, it requires numerous mounting and dismounting operations in order to exchange or replace certain printed boards and the possibilities of mounting printed boards of different kinds is limited. An optimal utilization of the space and thus a compact arrangement of printed circuit boards is not found in known control apparatuses.